Referring to FIG. 1, a prior art saw cover safety sensing device is illustrated. In this prior art, a machine table 1 is installed with an elevational frame 2 which is connected to a protecting cover 3. The height of elevation is in accordance with the width of the work piece. A saw is placed in the protecting cover 3. An inner front end of the protecting cover 3 is installed with an inner stop 4 for stopping undesired materials generated in sawing process. To avoid to hurt the hands of the operator, an infrared sensor 6 is installed in front of the protecting cover 3. As hands of the operator stretches into the sensing area of the infrared sensor 6, the saw will be stopped. However above mentioned prior art still has some defects which will be describe herein.
The sensing area is defined by one infrared line and thus the sensing area is too small to effectively protect the operator. On line sensing area causes that the saw must be stopped abruptly by very finite information and as a result, motor will be harmed gradually. The sensing principle is based on the hinder of the light beam, but if the light beam is hindered by human hand, the motor still stops. This will induce a trouble to users. The infrared sensor 6 is not combined to the protecting cover 3 and thus it cannot be adjusted with the protecting cover 3. Thus, it is inconvenient in operation.